Earlier this year ITU-T SG15/Q5 consented to a modified version of Recommendation G.655, “Characteristics of a Non-zero Dispersion-shifted Single-mode Optical Fibre (NZDSF) and Cable.” Among other things, two new tables were added with tightened chromatic dispersion specifications.
Previously, chromatic dispersion was described as a constant minimum and maximum value over the 1,530 to 1,565 nm C-band range. In reality, the chromatic dispersion of such fibers usually increases with wavelength. System experts requested more detailed information on this parameter for use in CWDM and DWDM recommendations.
|To address this request, SG15/Q5 surveyed commercially available NZDSF and agreed on the following modifications:|
The two new categories do not contain fibers with negative dispersion. These can still be referred to Table C of Rec. G.655 (type G.655.C). Although the older Tables A and B have not been included in the latest edition of G.655, they are still available in the 2003 edition.
The new edition of Recommendation G.655 (03/2006) was recently published and is available at the ITU-T web site (www.itu.int/rec/T-REC-G.655/en). To harmonize its standards with ITU, IEC SC86A is in the process of updating its singlemode-fiber product specification (IEC 60793-2-50, fiber type B.4).
Gerard Kuyt is product line manager at Draka Comteq Optical Fibre in The Netherlands, a delegate to ITU-T SG15/Q5, and convenor of IEC SC86A/WG1. He can be reached at email@example.com.